In a semiconductor device fabrication process, a wafer having a device area with a plurality of devices partitioned by a plurality of division lines is divided into individual dies. This fabrication process generally comprises a grinding step for adjusting the wafer thickness and a cutting step of cutting the wafer along the division lines to obtain the individual dies. In order to protect the devices formed on the wafer during this fabrication process and to suitably position the individual dies, an adhesive tape can be attached to the side of the wafer having the devices formed. thereon.
In known semiconductor device fabrication processes, such as flip chip packaging, Wafer Level Chip Scale Package (WLCSP) and Embedded Wafer Level Ball Grid Array (eWLB), the cutting step referred to above is performed from the front side of the wafer on which the devices are formed. In this cutting process, a surface layer, such as a low-k layer (i.e., a layer with low dielectric constant), formed on the wafer front side is first removed along the division lines by laser grooving. Subsequently, the wafer is fully cut along the resulting laser grooves by blade dicing from the front side of the wafer.
The grooves formed by this laser grooving process need to have a sufficient width for allowing the cutting blade to safely pass therethrough in the subsequent blade dicing step without damaging the remaining surface layer. Hence, the laser groove width is chosen to be significantly larger than the cutting width in the blade dicing process. This requirement of a relatively large laser groove width results in a wider spacing between neighbouring devices and thus limits the number of devices which can be arranged on the wafer, i.e., the packing density. Further, multiple laser passes are necessary to provide such a wide laser groove, thereby rendering the laser grooving process time-consuming and inefficient.
Therefore, the throughput of processed devices per hour is reduced and the productivity is lowered.
Moreover, due to the heat generated in the laser grooving process, the remainder of the surface layer, such as the low-k layer, formed on the front side of the wafer may at least partly delaminate, causing damage to the devices and/or the wafer substrate. Such damage may not only affect the functionality of the devices but also reduce the die strength of the resulting device chips.
Hence, there remains a need for a time- and cost-efficient wafer dividing method which allows for any risk of damage to the wafer to be minimised.